Investigate KSelect’s dropdown being displayed above the input in some cases even when there is enough space below

[MisRob]

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Summary

When there is enough space, KSelect's dropdown should be displayed below the input. However, there are several places in Kolibri where the dropdown is displayed above the input, even though there's enough space below. One example from Kolibri 0.17.0a0.dev0+git.123.g5cd1f6aa:

Coach → Plan → Lessons

This issue is present in other selects in Plan and Reports.

Interestingly, in a very similar place in Facility → Users, it works as expected:

The main culprit seems to be the bottom positioning set to 62px on .ui-select-dropdown. After commenting it out, the dropdown shows correctly in the Coach:

The bottom value is calculated in the calculateSpaceBelow method:

kolibri-design-system/lib/KSelect/index.vue

Lines 878 to 893 in 0cbdf57

	calculateSpaceBelow() {
	// Get the height of element
	const buttonHeight = this.$el.getBoundingClientRect().height;
	// Get the position of the element relative to the viewport
	const buttonPosition = this.$el.getBoundingClientRect().top;
	// Check if there is enough space below element
	// and update the "dropdownButtonBottom" data property accordingly
	const notEnoughSpaceBelow =
	buttonPosition > this.maxDropdownHeight &&
	this.scrollableAncestor.offsetHeight - buttonPosition <
	buttonHeight + this.maxDropdownHeight;
	this.dropdownButtonBottom = notEnoughSpaceBelow ? buttonHeight + 'px' : 'auto';
	},

The goal of this issue is to find out why exactly the calculation doesn't work well for places in the Coach (or check whether it’s overwritten from somewhere else, even though that’s rather unlikely). After we know more, we can determine the next steps and see if the calculation can be optimized.

References

Originally reported in learningequality/kolibri#12079 (not related to the refactor being tested there - the bug was present before).